ardupilot/libraries/AP_OpticalFlow/AP_OpticalFlow_MSP.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <AP_HAL/AP_HAL.h>
#include <AP_AHRS/AP_AHRS.h>
#include "AP_OpticalFlow_MSP.h"
#if HAL_MSP_OPTICALFLOW_ENABLED
#define OPTFLOW_MSP_TIMEOUT_SEC 0.5f // 2Hz
extern const AP_HAL::HAL& hal;
using namespace MSP;
// detect the device
AP_OpticalFlow_MSP *AP_OpticalFlow_MSP::detect(AP_OpticalFlow &_frontend)
{
// we assume msp messages will be sent into this driver
return new AP_OpticalFlow_MSP(_frontend);
}
// read latest values from sensor and fill in x,y and totals.
void AP_OpticalFlow_MSP::update(void)
{
// record gyro values as long as they are being used
// the sanity check of dt below ensures old gyro values are not used
if (gyro_sum_count < 1000) {
const Vector3f& gyro = AP::ahrs().get_gyro();
gyro_sum.x += gyro.x;
gyro_sum.y += gyro.y;
gyro_sum_count++;
}
// return without updating state if no readings
if (count == 0) {
return;
}
struct AP_OpticalFlow::OpticalFlow_state state {};
state.surface_quality = quality_sum / count;
// calculate dt
const float dt = (latest_frame_us - prev_frame_us) * 1.0e-6;
prev_frame_us = latest_frame_us;
// sanity check dt
if (is_positive(dt) && (dt < OPTFLOW_MSP_TIMEOUT_SEC)) {
// calculate flow values
const float flow_scale_factor_x = 1.0f + 0.001f * _flowScaler().x;
const float flow_scale_factor_y = 1.0f + 0.001f * _flowScaler().y;
// copy flow rates to state structure
state.flowRate = { ((float)flow_sum.x / count) * flow_scale_factor_x * dt,
((float)flow_sum.y / count) * flow_scale_factor_y * dt};
// copy average body rate to state structure
state.bodyRate = { gyro_sum.x / gyro_sum_count, gyro_sum.y / gyro_sum_count };
// invert flow vector to align it with default sensor orientation (required on matek 3901)
state.flowRate *= -1;
// we only apply yaw to flowRate as body rate comes from AHRS
_applyYaw(state.flowRate);
} else {
// first frame received in some time so cannot calculate flow values
state.flowRate.zero();
state.bodyRate.zero();
}
_update_frontend(state);
// reset local buffers
flow_sum.zero();
quality_sum = 0;
count = 0;
// reset gyro sum
gyro_sum.zero();
gyro_sum_count = 0;
}
// handle OPTICAL_FLOW msp messages
void AP_OpticalFlow_MSP::handle_msp(const MSP::msp_opflow_data_message_t &pkt)
{
// record time message was received
// ToDo: add jitter correction
latest_frame_us = AP_HAL::micros64();
// add sensor values to sum
flow_sum.x += pkt.motion_x;
flow_sum.y += pkt.motion_y;
quality_sum += (int)pkt.quality * 100 / 255;
count++;
}
#endif // HAL_MSP_OPTICALFLOW_ENABLED